RasGRP1 signaling is required for Vγ2+ thymocyte c-Maf expression and γδT17 lineage programming.

The γδ TCR instructively directs both lineage specification and effector programming of developing γδ T cells. However, the way in which different TCR signal strengths and other auxiliary signals coordinate downstream of the γδ TCR to regulate γδ T-cell development remains unclear. In this study we defined the role of Ras guanyl-releasing protein 1 (RasGRP1) in the development and effector programming of γδ T cells.

Spatial organization of pulmonary type 2 inflammation by a macrophage-derived cholesterol metabolite.

Effective pulmonary immunity requires the precise spatial organization of immune cells, yet the mechanisms guiding their intratissue positioning during inflammation remain unclear. Here, we identify a cholesterol-derived chemotactic axis that spatially organizes T helper 2 (T2) cells during fungal-induced pulmonary type 2 inflammation. Inflammation-expanded macrophages expressing cholesterol-25-hydroxylase (CH25H) produce 25-hydroxycholesterol, which is converted into the oxysterol 7α,25-dihydroxycholesterol to attract GPR183-expressing T2 cells into infectious lesions.

Investigating Murine CD4 T Cell Differentiation Using CRISPR-Cas9 Ribonucleoprotein Complex-mediated Gene Ablation.

The widespread accessibility of clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 technology has made gene targeting in primary cells a routine method for evaluating gene function in T cells. Given the cost and limited availability of knockout (KO) mouse strains, testing preliminary hypotheses involving gene function in T cells can be prohibitive using gene-targeted animal models. However, using commercially available resources, including predesigned guide RNAs (gRNAs), researchers can conveniently generate gene-targeted naïve T cells that can be used for T cell activation and differentiation studies.

Sulfide is a keystone metabolite for gut homeostasis and immunity.

Hydrogen sulfide is a gaseous, reactive molecule specifically enriched in the gastrointestinal tract. Here, we uncover a non-redundant role for sulfide in the control of both microbial and immune homeostasis of the gut. Notably, depletion of sulfide via both pharmaceutical and dietary interventions led to a profound collapse of CD4 T cells in the ileum of the small intestine lamina propria and significant impact on microbial ecology.

A PI3Kδ-Foxo1-FasL signaling amplification loop rewires CD4 T helper cell signaling, differentiation and epigenetic remodeling.

While inputs regulating CD4 T helper cell (Th) differentiation are well-defined, the integration of downstream signaling with transcriptional and epigenetic programs that define Th-lineage identity remain unresolved. PI3K signaling is a critical regulator of T cell function; activating mutations affecting PI3Kδ result in an immunodeficiency with multiple T cell defects. Using mice expressing activated-PI3Kδ, we found aberrant expression of proinflammatory Th1-signature genes under Th2-inducing conditions, both and .

Mind the GAP: RASA2 and RASA3 GTPase-activating proteins as gatekeepers of T cell activation and adhesion.

Following stimulation, the T cell receptor (TCR) and its coreceptors integrate multiple intracellular signals to initiate T cell proliferation, migration, gene expression, and metabolism. Among these signaling molecules are the small GTPases RAS and RAP1, which induce MAPK pathways and cellular adhesion to activate downstream effector functions. Although many studies have helped to elucidate the signaling intermediates that mediate T cell activation, the molecules and pathways that keep naive T cells in check are less understood.

Eosinophil trafficking in allergen-mediated pulmonary inflammation relies on IL-13-driven CCL-11 and CCL-24 production by tissue fibroblasts and myeloid cells.

Background: The immunologic mechanisms underlying pulmonary type 2 inflammation, including the dynamics of eosinophil recruitment to the lungs, still need to be elucidated.

Objective: We sought to investigate how IL-13-producing T2 effector cells trigger eosinophil migration in house dust mite (HDM)-driven allergic pulmonary inflammation.

Methods: Multiparameter and molecular profiling of murine lungs with HDM-induced allergy was investigated in the absence of IL-13 signaling by using IL-13Rα1-deficient mice and separately through adoptive transfer of CD4 T cells from IL-5-deficient mice into TCRα mice before allergic inflammation.

TCR-independent CD137 (4-1BB) signaling promotes CD8-exhausted T cell proliferation and terminal differentiation.

CD137 (4-1BB)-activating receptor represents a promising cancer immunotherapeutic target. Yet, the cellular program driven by CD137 and its role in cancer immune surveillance remain unresolved. Using T cell-specific deletion and agonist antibodies, we found that CD137 modulates tumor infiltration of CD8-exhausted T (Tex) cells expressing PD1, Lag-3, and Tim-3 inhibitory receptors.

Inherited human ITK deficiency impairs IFN-γ immunity and underlies tuberculosis.

Inborn errors of IFN-γ immunity can underlie tuberculosis (TB). We report three patients from two kindreds without EBV viremia or disease but with severe TB and inherited complete ITK deficiency, a condition associated with severe EBV disease that renders immunological studies challenging. They have CD4+ αβ T lymphocytopenia with a concomitant expansion of CD4-CD8- double-negative (DN) αβ and Vδ2- γδ T lymphocytes, both displaying a unique CD38+CD45RA+T-bet+EOMES- phenotype.

A CRISPR screen targeting PI3K effectors identifies RASA3 as a negative regulator of LFA-1-mediated adhesion in T cells.

The integrin lymphocyte function-associated antigen 1 (LFA-1) helps to coordinate the migration, adhesion, and activation of T cells through interactions with intercellular adhesion molecule 1 (ICAM-1) and ICAM-2. LFA-1 is activated during the engagement of chemokine receptors and the T cell receptor (TCR) through inside-out signaling, a process that is partially mediated by phosphoinositide 3-kinase (PI3K) and its product phosphatidylinositol 3,4,5-trisphosphate (PIP). To evaluate potential roles of PI3K in LFA-1 activation, we designed a library of CRISPR/single guide RNAs targeting known and potential PIP-binding proteins and screened for effects on the ability of primary mouse T cells to bind to ICAM-1.

γδ Thymocyte Maturation and Emigration in Adult Mice.

Several unique waves of γδ T cells are generated solely in the fetal/neonatal thymus, whereas additional γδ T cell subsets are generated in adults. One intriguing feature of γδ T cell development is the coordination of differentiation and acquisition of effector function within the fetal thymus; however, it is less clear whether this paradigm holds true in adult animals. In this study, we investigated the relationship between maturation and thymic export of adult-derived γδ thymocytes in mice.

PI3K in T Cell Adhesion and Trafficking.

PI3K signalling is required for activation, differentiation, and trafficking of T cells. PI3Kδ, the dominant PI3K isoform in T cells, has been extensively characterised using PI3Kδ mutant mouse models and PI3K inhibitors. Furthermore, characterisation of patients with Activated PI3K Delta Syndrome (APDS) and mouse models with hyperactive PI3Kδ have shed light on how increased PI3Kδ activity affects T cell functions.

Human islets contain a subpopulation of glucagon-like peptide-1 secreting α cells that is increased in type 2 diabetes.

Objectives: Our study shows that glucagon-like peptide-1 (GLP-1) is secreted within human islets and may play an unexpectedly important paracrine role in islet physiology and pathophysiology. It is known that α cells within rodent and human pancreatic islets are capable of secreting GLP-1, but little is known about the functional role that islet-derived GLP-1 plays in human islets.

Methods: We used flow cytometry, immunohistochemistry, perifusions, and calcium imaging techniques to analyse GLP-1 expression and function in islets isolated from cadaveric human donors with or without type 2 diabetes.

Differential expression of interferon-lambda receptor 1 splice variants determines the magnitude of the antiviral response induced by interferon-lambda 3 in human immune cells.

Type III interferons (IFN-lambdas(λ)) are important cytokines that inhibit viruses and modulate immune responses by acting through a unique IFN-λR1/IL-10RB heterodimeric receptor. Until now, the primary antiviral function of IFN-λs has been proposed to be at anatomical barrier sites. Here, we examine the regulation of IFN-λR1 expression and measure the downstream effects of IFN-λ3 stimulation in primary human blood immune cells, compared with lung or liver epithelial cells.

Thymic progenitors of TCRαβ CD8αα intestinal intraepithelial lymphocytes require RasGRP1 for development.

Strong T cell receptor (TCR) signaling largely induces cell death during thymocyte development, whereas weak TCR signals induce positive selection. However, some T cell lineages require strong TCR signals for differentiation through a process termed agonist selection. The signaling relationships that underlie these three fates are unknown.

RasGRP1 and RasGRP3 Are Required for Efficient Generation of Early Thymic Progenitors.

T cell development is dependent on the migration of progenitor cells from the bone marrow to the thymus. Upon reaching the thymus, progenitors undergo a complex developmental program that requires inputs from various highly conserved signaling pathways including the Notch and Wnt pathways. To date, Ras signaling has not been implicated in the very earliest stages of T cell differentiation, but members of a family of Ras activators called RasGRPs have been shown to be involved at multiple stages of T cell development.

RasGRP1, but not RasGRP3, is required for efficient thymic β-selection and ERK activation downstream of CXCR4.

T cell development is a highly dynamic process that is driven by interactions between developing thymocytes and the thymic microenvironment. Upon entering the thymus, the earliest thymic progenitors, called CD4(-)CD8(-) 'double negative' (DN) thymocytes, pass through a checkpoint termed "β-selection" before maturing into CD4(+)CD8(+) 'double positive' (DP) thymocytes. β-selection is an important developmental checkpoint during thymopoiesis where developing DN thymocytes that successfully express the pre-T cell receptor (TCR) undergo extensive proliferation and differentiation towards the DP stage.